Electric incandescent lamp with shock and vibration resistant filament support structure



April 29, 1969 w. H. HOUG'H 3,441,770

, ELECTRIC INCANDESCENT LAMP WITH SHOCK AND VIBRATION.

masxsmm FILAMENT SUPPORT STRUCTURE Filed April 10. 1967 lnventoT-iWiLF'T'fiBd I-I. Hough by 62%- f His Arm-Q hey United States Patent3,441,770 ELECTRIC INCANDESCENT LAMP WITH SHOCK AND VIBRATION RESISTANTFILAMENT SUP- PORT STRUCTURE Wilfred H. Hough, Cleveland Heights, Ohio,assignor to General Electric Company, a corporation of New York FiledApr. 10, 1967, Ser. No. 629,461 Int. Cl. H01k 1/30 US. Cl. 313-113 8Claims ABSTRACT OF THE DISCLOSURE In an incandescent lamp, especially ofthe sealed-beam type, having a filament supported on lead-in wires whichare tied together by a bridge and are formed below the bridge intospring portions which permit the filament, lead wires and bridge to flexas a unit in all directions, there is provided a resilient damper wirewhich extends transversely of the bridge with its ends engaging the bulbwall at opposite sides thereof and which has its mid-portionfrictionally engaged by the bridge and held thereby in a depressed orbowed position.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to electric incandescent lamps comprising a sealed envelopecontaining an incandescible filament, and is particularly concerned withlamps which are adapted for use in service conditions where they aresubjected to shock and vibration.

Description of the prior art Although the invention is not limitedthereto, it will be described herein with particular reference to lampsof the so-called sealed-beam type and which are used in railway service,particularly train warning lamps which are used on railway switchlocomotives in a fixture which rotates two or three lamps to produce awarning flashing signal. To handle roadbed and engine vibration alongwith shock occasioned by coupling of the engine with other equipment,the lamp must be able to withstand vibration and shock in all directionswithout distortion and premature destruction of the filament.

Some success has been achieved heretofore by forming each of the lead-inconductors in separate sections spaced apart longitudinally andelectrically and mechanically interconnected by a coiled springelastically fitted over and bridging the gap between the sections, as inPatent 2,497,567 to J. E. Stone, or by forming intermediate portions ofthe lead-in wires with laterally extending and opposed arcuate sectionsof semicircular shape which serve as a cushion or spring, as in Patent2,497,566 to J. E. Stone et al. In a further attempt to avoid theadverse effects of extreme shock conditions, lamps of thefirst-mentioned type were provided with bumper or stop members in theform of rigid wires fixed at their center to respective lead wires,extending laterally of the plane including the filament and lead-inwires, and terminating at each end a short distance from the curvedreflector surface of the lamp whereby to limit the deflection of thefilament mount structure to a degree less than that which would cause itto take a permanent set.

SUMMARY OF THE INVENTION It is an object of the invention to provide animproved construction which will materially improve the service life oflamps which are subjected to severe shocks and vibration.

Accordingly, in accordance with the invention, there is provided aconstruction in which the filament and its adjacent supporting structureis supported by spring means which leaves it free to vibrate in alldirections and additionally, there is provided a damper means whichfunctions as a true mechanical damper by imparting friction to thevibrating filament supporting structure whereby it settles back almostimmediately when displaced in any direction.

In accordance with a preferred aspect of the invention, the damper is inthe form of a length of resilient or springy wire which extendstransversely of the filament supporting structure with its opposite endsengaging the wall of the lamp envelope and which is frictionally engagedat its mid-section by the filament supporting structure and held therebyin a depressed or bowed position against the action of the more powerfulfilament supporting spring means so that it is always ready to performits damping action irrespective of the direction of displacement orflexure of the filament supporting structure.

BRIEF DESCRIPTION OF THE DRAWING Further features and advantages of theinvention will appear from the following detailed description of aspecies thereof and from the drawing wherein:

FIG. 1 is a tilted view of a lamp having a resilient filament supportingand damping construction in accordance with the invention; and

FIG. 2 is a section through the lamp in a plane which includes one ofthe 1ead-in wires and is normal to the plane which includes the filamentand both of its supporting lead-in wires.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, thelamp illustrated therein is of the sealed-beam type comprising anenvelope consisting of a pressed glass concave reflector section 1 and apressed glass cover or lens section 2 which are hermetically sealedtogether at their peripheries. The interior surface of the reflectorsection 1, which may be of paraboloidal or any other desired opticalshape, has thereon a reflecting coating 3 which may be of a metal suchas vapor-deposited aluminum or silver.

The reflector section 1 carries a terminal structure which comprises apair of metal ferrules or thimbles 4 having feathered edges which arehermetically sealed and embedded in the thickness of the glass section 1around the margins of openings -5 therein, so that said ferrulesconstitute part of the envelope wall. The envelope 1, 2, is exhaustedand preferably gas-filled, through an aperture 6 (FIG. 1) at the apex ofthe reflector section 1, by way of an exhaust tube (not shown) which issealed to the exterior of said reflector section in communication withthe aperture 6 and is ultimately sealed or tipped off close to theenvelope wall.

The envelope contains a filament 7 which is here illustrated as ahelical coil of tungsten wire which extends transversely across theoptical axis of the reflecting surface 3. The filament 7 is connected atits ends to the inner end portions 8 of a pair of lead-in conductors 9which extend into the envelope in parallel spaced relationship fromrespective ferrules 4 in which the outer end portions 10 of the leads 9are secured, for example by a quantity 11 of solder or brazing material.The inner portions 8 of the lead-in conductors are insulatively andrigidly tied together by a suitable bridge means, here illustrated ascomprising a glass rod 12 which carries at each end a pair of spacedsupport Wires 13 having one end embedded in the rod 12 and the other endsecured, as by welding, to the adjacent inner lead wire portion 8.Supplemental filament support wires 14 each has one end embedded in therod 12 and the other end looped about an intermediate portion of thefilament 7.

The filament 7, upper lead wire portions 8 and bridge 12 are resilientlysupported for flexure in any direction by the provision of suitablespring means. As herein illustrated by way of example, the lead-inconductors 9 are made of a suitable springy material and are formed withintegral intermediate helically coiled portions 15. For that purpose,the lead wires 9 may be made of a material such as stainless steel,molybdenum, tungsten or, preferably a copper base alloy containingzirconium and sold under the trademark Amzirc by Climax MolybdenumCompany.

Although the resilient supporting structure thus far described is quiteeffective in minimizing damage to the filament 7 when the lamp issubjected to shock and vibration, still further improvement is obtainedin accordance with the invention by the provision of a damper means. Thedamper member is in the form of a normally straight length of resilientwire 16 which extends transversely of the bridge member 12 with its endsengaging the wall of the reflector section 1 of the envelope at oppositesides thereof and adjacent its periphery, and with its midportionengaged by the composite bridge means 12, 13 and held thereby in adepressed position so that the wire is bowed downwardly toward the apexof said reflector section 1 and the anchored ends of the lead-inconductors 9.

The damper wire may be located as shown by the broken lines 16a in FIG.1 where it is engaged by the glass bridge rod 12 substantially at thecenter thereof and its ends are held down against the edges of anannular shoulder 17 at the periphery of the envelope reflectorsection 1. Although good results may be obtained with the damper wire16a so located, it is possible that under conditions of severe shock andvibration, the wire 16a may shift its position away from the normal tothe bridge member 12, even to such a degree that it assumes a positionvirtually parallel to the bridge member 12 where it comes into shortcircuiting engagement with the lead-in conductors 9. Such an extremedegree of shifting of the damper wire 16a may be prevented by fixedlytacking or sealing one end thereof to the wall of the envelope section1, or even securely sealing one end in the rim of the envelope betweenthe peripheral sealing surfaces of the envelope sections 1 and 2. Theother end of the damper wire 16a must, in that event, remain free to rubagainst the surface of the envelope wall so that the wire is free toflex upon movement of the assembly of bridge 12, filament 7 and innerlead wire portions 8.

However, in a presently preferred arrangement, the damper wire 16 islocated to extend between the spaced pair of support wires 13 at one endof the bridge where it is frictionally engaged at its mid-point by oneof those wires. Such an arrangement avoids the shifting of the wire 16to the degree referred to above in connection with a wire located at16a. It is preferred that both ends of the wire 16 be in free frictionalengagement with the envelope wall. However, if desired, one end of wire16 may be tacked or sealed to the envelope wall. The wire 16 may be madeof a material of such size and composition that it is sufficientlyresilient or springy to perform its damping function. To that end, thewire 16 is preferably made of molybdenum, although tungsten is alsoquite suitable.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electric incandescent lamp comprising a sealed envelope, a.filament in said envelope, lead-in conductors anchored to and supportedfrom the wall of said envelope and extending into the envelope in thesame general direction and connected at their inner ends to saidfilament, bridge means extending between and insulatively and rigidlytying together the inner end portions of said lead-in conductors, saidlead-in conductors being provided intermediate their anchored ends andsaid bridge means with resilient spring means permitting flexure of thefilament and inner ends of the lead-in conductors as a unit in alldirections, and damper means comprising a resilient wire member whichextends transversely of said bridge means with its ends engaging thebulb wall at opposite sides thereof and with its mid-portionfrictionally engaged by said bridge means and held thereby in adepressed position so that said wire is bowed downwardly toward theanchored ends of the lead-in conductors, at least one of the ends ofsaid wire member being free to rub against the envelope wall uponflexure of said wire member.

2. A lamp as set forth in claim 1 wherein said bridge means comprises aglass rod having a pair of spaced support wires secured to each endthereof and projecting therefrom toward and secured to an adjacent oneof said lead-in conductors, and said resilient damper wire has its saidmid-portion located between one of said pair of spaced support wires.

3. A lamp as set forth in claim 2 wherein said resilient spring means isa helically coiled spring portion of each of the lead-in conductors.

4. A lamp as set forth in claim 1 wherein said resilient spring means isa helically coiled spring portion of each of the lead-in conductors.

5. An electric incandescent lamp of sealed beam type comprising a sealedenvelope including a concave reflector section and a cover glass sectionsealed at their peripheries, a filament in said envelope, lead-inconductors anchored to and supported from the wall of said reflectorsection adjacent its apex and extending into the envelope in the samegeneral direction and connected at their inner ends to said filament,bridge means extending between and insulatively and rigidly tyingtogether the inner end portions of said lead-in conductors, said lead-inconductors being provided intermediate their anchored ends and saidbridge means with resilient spring means permitting flexure of thefilament and inner ends of the lead-in conductors as a unit in alldirections, and damper means comprising a resilient wire member whichextends transversely of said bridge means with its ends engaging thewall of said concave reflector section of the envelope at opposite sidesthereof and adjacent its periphery and with its mid-portion frictionallyengaged by said bridge means and held thereby in a depressed position sothat said wire is bowed downwardly toward the apex of said reflectorsection, at least one of the ends of said wire member being free to rubagainst the envelope wall upon flexure of said wire member.

6. A lamp as set forth in claim 5 wherein said bridge means comprises aglass rod having a pair of spaced support wires secured to each endthereof and projecting therefrom toward and secured to an adjacent oneof said lead-in conductors, and said resilient damper wire has its saidmid-portion located between one of said pair of spaced support wires.

7. A lamp as set forth in claim 6 wherein said resilient spring means isa helically coiled spring portion of each of the lead-in conductors.

8. A lamp as set forth in claim 5 wherein said resilient spring means isa helically coiled spring portion of each of the lead-in conductors.

References Cited UNITED STATES PATENTS 2,497,567 2/1950 Stone 3l327l2,633,548 3/1953 Kramel 313113 2,824,995 2/1958 Kirk 313271 3,114,06912/1963 Peek et a1 3l3269 3,270,238 8/1966 Mosby 313279 3,375,393 3/1968Morgan 313-278 X JAMES W. LAWRENCE, Primary Examiner.

E. R. LA ROCHE, Assistant Examiner.

US. Cl. X.R. 313-269, 271, 278

